I have not dealt with this seller personally so looking at feedback, having an actual phone conversation, etc. is advisable when making a purchase like this.
When it comes to 204 although I never heard it, the use of switch mode power supply is an immediate deal breaker for me. Having had the Qutest and the TT2 I am familiar witj how sensitive these DACs are to power. Yes you can get the upgraded Weiss linear power supply but why the need for two boxes?
Your $5,000 budget is good enough to get an excellent DAC. The 501 uses linear power supply and is a single box. Other DACs to consider in this price range - Bricasti, Meitner, Denafrips Terminator, Holo Audio May KTE, etc